Such a piston is known from published German patent application 35 13 839. In this case, the piston consists of a piston carrier adapted to be connected rigidly to the piston rod, and a piston ring disposed to be axially movable between two abutments on the piston carrier. The inside diameter of the piston ring is in this case slightly smaller than the outside diameter of an abutment. By reason of this development, the piston ring can be mounted on the piston carrier in that the piston ring is pushed over this abutment. The piston carrier which consists of rigidly resilient synthetic plastics material is so deformed in the process that the piston ring snaps into place in the piston ring groove. The abutment surface which the piston ring offers to this abutment is certainly very small so that it is impossible to preclude a risk of the piston ring not being reliably held in the piston ring groove between the abutments.
It is known from U.S. Pat. No. 4,307,873 to dispose a piston on a piston rod in such a way as to be axially displaceable, the piston having resilient projections which engage over a piston ring fixed on the piston rod by rivets, so that the piston is secured against falling out and off the piston rod.